Well treating apparatus



Nov. 17, 1959 E. D. AYERS WELL TREATING APPARATUS Filed April 4, 1956INVENTOR Ear/D. ge/S BY HTTONE YS ire This invention relatesto a methodof and apparatus for selectively operating through the same electricalconductors of a supporting cable two electrically operated bore holelogging or treating devices.

Oil or gas wells are often completed by running casing to the bottom ofthe bore hole and then forcing cement through the casing and into thespace between the well bore wall and the casing. Cementing the casing inplace in the well bore effectively prevents uids emanating from one ormore strata along the well bore from contaminating other strata.However, the cementing operation usually seals ott the oil producingstrata as well as those strata which are capable of producing undesirediluids or which are capable of absorbing fluids.

Customarily the casing and cement are perforated adjacent to the oilproducing strata in order to permit oil from the producing strata toenter the casing. Perforation of the casing and well bore wall(including cement) is usually accomplished by suspending a perforatinggun from a suitable electric cable and lowering the gun into the wellbore until the gun is beside the producing formation, and then ring thegun.

Although the depth below the earths surface of the producing formationis usually known from data taken as the well is drilled, it is notcustomary to rely on such data in determining where the casing is to beperforated. Usually a radioactivity log is made of the formationsadjacent to the well bore and the perforating gun is disposed, for ring,at a depth indicated by the well survey of the radioactivity of theformations. This has, in the past, been somewhat time consuming in thatthe Well bore logging device is first lowered into the well bore `tomake the log of radioactivity of the adjacent formations and then mustbe removed from the well bore before the perforating gun is lowered intothe well bore. Usually the well bore logging device and the perforatinggun are lowered on the same cable (although at different times) inorder. to avoid possible errors in depth measurement which might occurif two diierent cables were used.

Accordingly, a principal object of this invention is to provide animproved apparatus and method for selectively operating a well boresurveying device and a well bore perforating gun from the sameelectrical conductors of a cable containing at least two electricalconductors, one` tector and the perforating device are disposed side bysidel as they are lowered into the well bore. The radiation detector hasan anode which is connected directly to the insulated conductor and aycathode which is connected to a detonating means requiring a relativeheavy current (as '2,912,932 Patented Nov. 17, 1959 compared to thedetector current) to tire it. The detonating means is connected to aground return conductor. When the desired radiation pattern is receivedand identified through radiation counting apparatus located at thesurface, the potential on the cable is increased suciently to break downthe radiation detector and re the perforating device. Both the radiationdetector and `the perforating device are made of frangible materialwhich is broken into small pieces by the explosion of the perforatingdevice.

The invention, as well as additional objects and advantages thereof,will best be understood when the following detailed description is readin connection with the accompanying drawing, in which:

Fig. l shows, in diagrammatical form, the apparatus of this invention.

Referring to the drawing, there is shown a well bore, indicatedgenerally by the numeral lt), extending from the surface l2 of the earththrough various strata or earth formations 14, 14a, Mb. The well borecontains a string of casing i6 which extends from the earths surface 12to near the bottom i3 of the well bore 1t). The space between the casing16 and the wall 20 of the well bore is filled with cement 21 from thebottom 18 of the well bore to the earths surface l2, for example.

Disposed within the well bore lil is a cable, indicated generally by thenumeral 22, which includes an inner, insulated conductor 24 and agrounded conductor 26 which yis commonly, but not necessarily, the metalsheathing or load carrying part of the cable 22.

Above the surface l2, the cable 22 passes over a sheave 27 supported bya derrick 2S and is coiled onto a reel 39. The inner conductor 24' isconnected to a commutator element 32 on the reel 3) and electricalconnection to the insulated conductor 24 of the cable 22 is made througha brush contact member 34. As illustrated in the drawing it is assumedthat the outer conductor 26 is the metal, load carrying outer part ofthe cable 22 and that the conductor 26 is grounded, as indicated by theground connections 36, 38 at any convenient point, as through the reel39 and derrick 28 to the earth 12, for example.

A perforating gun, indicated generally by' the numeral 40, and aradiation detector, a Geiger-Muller tube, indicated generally by thenumeral 42, are attached at the lower end 44 of the cable 22. The gun 40and tube 42 are, in practice, physically disposed side by side. Theanode 46 of the tube 42 is electrically connected to the inner orinsulated conductor 24- of the cable 22. The cathode 48 of the tube iselectrically connected to the detonating means of the gun 4G, commonly ablasting cap S0 requiring an ampere or more of current to detonate it.The blasting cap 50 also is electrically connected to the ground returnconductor 26 by any convenient means such as the ground `connection 52.

A fuse 54 which is capable of carrying current of the order of a fewmilliamperes is connected in shunt across the detonatng means 50. Acondenser 56 is also connected in shunt across the detonating means 50.Although the detonating or tiring means 50 for the perforating gun 40may be a blasting cap, other current actuated devices such as aresistance heating element (not shown) adapted to ignite a powder chargeupon the passage through the element of a specified current may be usedin ring the gun 40.

A power source, indicated generally by the numeral 6G, is illustrated astwo batteries 62, 64 connected in series with the cathode of the battery64 grounded, as at 66.

The lead 68 connects the two batteries 62, 64 to a terminal of amultiple terminal switch 70. The lead 72 connects the anode of thebattery ,62 to another terminal of the Switch 70. The switch 70 iscoupled through a series resistor 74 and lead 76 to the commutator brush34. A switch 78 is connected in parallel with the resistor 74 andpermits the resistor '74 to be lay-passed, for reasons which will beexplained later.

A pulse count indicator 80, which may be energized by any suitablesource of power (not shown) is connected to ground as indicated by theconnection 82 and is coupled to the commutator bar 34 through the lead84 and the condenser 86.

In operation the perforating gun y4t) and radiation detector 42 areattached to the end 44 of the cable 22 with electrical connectionsbetween the conductor 24 and the gun 40 and detector 42 being madethrough suitably enclosed connectors (not shown) to prevent the innerconductor 24 of the cable 22 from being grounded directly and notthrough nthe desired loads (tube 42 and gun 40). VThe radiation detector42, a Geiger-Muller tube, is energized by connecting the arm 88 of theswitch 70 to the anode lead 68 of the battery 64. It will be assumedthat the battery 64 provides a direct current potential, say 1'000volts, which is sufficient to energize and operate the tube 42 but isnot sufficient to break down the tube and cause it to conduct heavily,thus tiring the detonator means. The fuse 54, which will safely carrythe current needed to operate thetube 42, shunts current around thedetonating means 50 to the ground return conductor 26 through the groundconnection 52.

With the radiation detector energized, the detector 42 and gun 40 aremoved up and down the well bore 10V to determine the radioactivity ofthe adjacent earth formation.

v22 and are coupled through the lead 84 and condenser 86 to a pulsecount indicator 80 of suitable design.

When the radioactivity survey indicates that the gun 4t) and detector 42are disposed beside the desired earth series) of the power source 60isapplied across the radiation detector 42 and across the detonatingmeansV 50, fuse 54, and condenser 56. The Geiger-Muller tube 42 breaksdown and conducts heavily when the higher gun tiring potential isapplied across the tube 42, thus permitting aisuiicient current to passthrough theV detonator means 50 to permit the tiring of the gunr40.

When the full potential, say 2,00() volts, of the power source 60 isapplied to the ringsource, the tube 42y ionizes and breaks down,applying the full potential of the power source 60 across the detonatingor'tiring means 50.V Under such conditionsA suflicient current ows toblow the fuse 54, causing all the current to flow through the `tiringmeans 5t), usually a blasting Vcap which res when an ampere of currentpasses thro'ughV it, to fire the perforating gun 40. The perforating gun40 may be ofV the structural type shown in `U.S. Patent No. 2,733,657 toC. M. Bryant et al., forexample, whichhas incorporated thereindetonating means of the blasting cap type requiring an ampere or more ofcurrent to detonate it."

The charges of the gun, which usually are of the Well known shapedcharge typejperforate the casing and cement when iirCCL permitting uidyfrom the adjacent earth ,formations 14' tok ow into lthe Vcasing 16.lThe explosion attendant to the tiring of the gun 4u normally shattersthe gun 40 and theV Geiger-Muller tube 50,'

As gamma rays from the Various formations strike the detector 42, pulsesare transmitted up the cable leaving no large sections of material tointerfere with the later operation of the well` The perforating gun 40and Geiger-Muller tube 42 are described heretofore as being disposedside-by-side. The Geiger-Muller tube 42, however, may be disposed eitherabove or below the gun 40. Thus, in operation of the invention when thedetector tube 42 is not beside the gun 40, the zone or strata to 'beshot is located by the detector tube 42 and the gun is then raised orlowered a short distance to the indicated shooting position. Anexplosive charge, adapted to detonate when the gun 40 is tired, shouldbe provided adjacent to the tube 42 to insure that no large pieces ofthe tube 42 remain to clog the bore hole after the gun 40 is tired.

Further, a rectified alternating current power source, suitablyfiltered, may be substituted for the batteries 62, 64 of the powersource 60.

The Geiger-Muller tubel may be made of glass tubing, having a lwireanode axially disposed therein and a cathode electrode Vdisposed alongthe inner wall of the tube.

The tube is illed with a suitable gas Vat a suitable pres-Y sure, as iswell known in the art of making Geiger-Muller tubes, to permit thekoperation of the tube at a desired structures permit their breaking downand conducting suflicient current to iire the gun 40 at potentialswithin the limitation of insulation of the cable 22.

The resistor 74, mentioned before, is inserted in series with the lead76 to the commutator brush 34 to prevent enough current `being passedthrough the conductor 24 to iire the perforating gun 40 in event thefull output of the power source 60 were accidentally applied to theconductor 24. The switch 78 permits the shorting out of the resistor 74when it is desired to ire the gun 40.

The fuse 54 is not necessary for the operability of this invention, butserves at least a psychological purpose in shunting current around thering means Sti even though the current used-in operating the tube 42would be in` suliicient to detonate the firing means.

' p It is thus apparent that this invention provides a simple means forlocating a perforating gun 40 opposite a desired earth formation 14a asthe gun 40 is lowered in a well bore 10. This invention eliminates theusual time consuming separate radioactivity survey run into the wellbore 10 and permits survey and firing of the perforating gun to bedone-in one instrumentrun into the well bore.

I claim:

1. Apparatus for locating a desired earth formation 'which is penetratedby a well bore, for positioning an Velectrically connected to saidinsulated conductor, said cathode beingelectrically connected to one ofthe leads of said firingmeans, the other of said ieadsjof said ringmeans being electrically connected to said ground return conductor, Varadiation pulse count indicator, means coupling said pulse countindicator to said insulated conductorofrsaid cable, a power-*sourcehaving high and intermediate outputV potentials, and means forselectively applyingsaid potentials ybetween said insulated conductorand said ground return conductor. y

2l Apparatus inraccordance with claim l, whereinsaid i' currentactuated'iiring means is a blasting cap which is capable of beingdetonated on thefpassage therethrough of current o'f the orderof oneampere.

means.

6. Apparatus in accordance with claim l, wherein said means forselectively applying said potentials includes a resistor connected inseries with said power source and said insulated conductor and a switchfor selectively shunting out said resistor.

References Cited in the le of this patent UNITED STATES PATENTS2,309,835 Fearon Feb. 2, 1943 2,349,041 Hare May 16, 1944 2,703,053Castel Mar. 1, 1955 2,732,518 Bricaud Ian. 24, 1956 2,736,260Schlumberger Feb. 28, 1956

